1. Field of the Invention
This invention pertains to the general field of hand trucks used to lift and move heavy weights in warehouses and similar environments. In particular, it provides a new and improved way of lifting and transporting barrels and drums of different sizes over variable terrain conditions.
2. Description of the Prior Art
People have used carts and similar kinds of apparatus to help them move heavy weights ever since the wheel was invented. Similarly, they have strived to develop equipment that makes it easier to secure the weight and load it on the moving device.
Hand trucks, also commonly called dollies, are the type of equipment developed over the years to pick up and move heavy objects within short distances. In principle, they all consist of a platform with a set of wheels at one end and long handles at the other. The weight is secured to the platform while it stands in a generally vertical position with the wheels on the ground; then, the weight can be lifted by pulling on the handles and using the length of the platform as a lever having the axle of the wheels as its fulcrum of leverage.
As early as 1893, in U.S. Pat. No. 499,212, Coffield describes an improved model of hand truck featuring a bottom shoe for holding the object being transported and an adjustable latch for securing it to the platform. These are still the basic features found in a modern all purpose dolly.
In U.S. Pat. No. 1,820,728 (1931), Calis shows a hand truck of different and novel construction, specifically designed for garbage cans and other barrel-shaped objects. The device consists of a single piece frame, two wheels and a load retainer capable of adjustment by sliding along the length of the frame.
U.S. Pat. No. 2,360,858 to Ernst (1944) discloses a piece of equipment for handling drums and comparable objects. Not strictly a dolly, the device consists of a vertical boom rigidly mounted on a horizontal frame on wheels. The boom is equipped with a latch for grabbing the load and a rack and pinion mechanism for raising and lowering it to various elevations.
In U.S. Pat. No. 2,447,300 (1948), Williams describes a device for grasping and holding in place container drums. The invention clamps the top flange of the drum between a hook and a supporting stop and secures the load to the equipment used to move it. Therefore, it is used in combination with hand trucks and elevator trucks as the means for engaging the load to the equipment.
Ernst shows an improved grasp device for hand trucks in U.S. Pat. No. 2,635,775 (1953). It is designed to improve the retention capability of such devices, especially for use on uneven floors, where the probability of failure of the locking mechanism can result from a rough ride and cause dangerous spills. As in Williams' invention, the apparatus is directed primarily to equipment for lifting and transporting barrels and drums. In U.S. Pat. No. 3,794,371 (1974), Arbouw describes a novel drum gripper used to hoist barrels into an upright position. The device is not applied in cooperation with hand or elevator trucks.
U.S. Pat. No. 3,815,767 to Lund et al. (1974) discloses a drum handling device that permits its positioning for optimal drainage. The apparatus consists of a standard dolly with an adjustable gripping mechanism for the chime of the drum; in addition, it features supporting bearings on its frame for rotating the drum for complete drainage while tilted to a near horizontal position. The frame of the dolly also contains members providing an appropriate structure to support the drum in that position.
Morissette, in U.S. Pat. No. 4,257,729 (1981), shows a hand truck for transporting loads without having to tilt them prior to positioning them on the truck. The platform of the dolly is provided with an adjustable clamp to grab the top of the load and with feet that rest on the ground when the dolly is positioned vertically against the object to be moved. While the dolly is in that position, its wheels are slightly elevated from the ground, so that they do not provide immediate support when the handle is pulled toward the operator to load the object on the platform. Rather, the pivotal point remains the bottom edge of the object itself, so that the object can be tilted with the platform, without lifting, until the tilting motion of the platform itself brings its wheels into contact with the ground. At that point, the pivot switches to the axle of the wheels and the object can be lifted after being already positioned on the truck.
U.S. Pat. No. 4,685,713 to Van der Hulst et al. (1987) describes a container grab of general application in hand trucks and elevator devices. The apparatus uses a novel clamping mechanism for container rims and multiple adjustments for holding a load in place.
Berg shows a powered drum lifting truck in U.S. Pat. No. 4,741,659 (1988). It consists essentially of a dolly frame with means for securely grabbing the upper rim of a drum. It also provides a mechanism for lifting the load while attached to the frame of the dolly to allow the operator to deposit it at different elevations.
Finally, various embodiments of the inventions described in these patents are found in current catalogs of material handling equipment. See, for example, Rand's 90-1 Catalogue at pages 144 and 145; and Ryerson's Wholesale Industrial catalog No. 119 at page 69.
The main objective in the operation of a hand truck is the ability of the operator to lift the load and position its weight on the axle of the wheels single-handedly and safely. In order to optimize the force available to the operator, the principle of the lever is used. The hand truck is built with long handles that enable the operator to exert leverage on the load attached to it by pivoting around the wheels' axle. By positioning and securing the frame of the hand truck vertically against the object to be moved, it becomes possible for a single person to lift it by pulling the handles away from the object, thus causing the entire assembly to pivot around the wheels. As a result, a single operator can lift and transport very heavy objects that could not otherwise be moved by one person alone.
The main problem with the hand trucks and similar pieces of equipment described in prior art is that the initial effort required to pull a load away from the ground onto the platform of the dolly is often beyond the ability of the average person. This difficulty is ameliorated by positioning the axle of the wheels as close as possible to the ground and to the load, so that the counterleverage exerted by the weight of the object is minimized. These design characteristics, though, have the negative effect of necessarily resulting in very small wheels which affect the smoothness of ride and the stability of the hand truck. Furthermore, and most importantly with regard to this invention, the do not eliminate the need to actually lift the load from the ground before the hand truck can begin cooperating with the load to facilitate its transport.
It is the purpose of this invention to address these problems. Accordingly, a modified frame is disclosed with a novel structure that optimize the cooperation between the carrying platform and the wheels in order to produce the maximum lifting force possible for the operator. In addition, because the invention minimizes the impact of the size of the wheels on the lifting action, it is possible to use large wheels and thus improve the rideability and stability of the truck.